# Immunogenicity of one and two doses of Gardasil®9 in Tanzanian girls in the DoRIS Trial

## TL;DR

This study shows that one or two doses of the Gardasil®9 vaccine in Tanzanian girls provide strong and lasting immune responses against multiple HPV strains.

## Contribution

The study provides long-term immunogenicity data for one and two doses of Gardasil®9 in a low-resource setting.

## Key findings

- One-dose recipients showed high seropositivity for most HPV strains, with immune responses stable through 36 months.
- Two-dose recipients had higher geometric mean concentrations and full seropositivity for all tested HPV strains.
- Immune responses from the vaccine are expected to continue for at least nine years post-vaccination.

## Abstract

Tanzanian girls received one to three doses of Gardasil®9 in the DoRIS randomised trial. Blood samples from one and two-dose Gardasil®9 recipients were collected at months (M)0, M7, M12, M24, and M36 for testing via an HPV Multiplex immunoassay. All participants were HPV 16, HPV 31, and HPV 58 seropositive at M36. For the one-dose group, 96.8–98.2% of girls were seropositive for HPV 11, HPV 18, and HPV 33 and 73.0-87.7% seropositive for HPV 6, HPV 45 and HPV 52. For the two-dose group, all participants were HPV 6, HPV 11, HPV 18, and HPV 33 seropositive, while 98.6% seropositive for HPV 45 and HPV 52. Geometric mean concentrations (GMCs) were higher in the two-dose group compared to the one-dose group but all GMCs in the one-dose group had plateaued by M24 and remained stable to M36. HPV vaccine immune responses in this study will continue through nine years post-vaccination. ClinicalTrials.gov ID: NCT02834637; Registration Date: 2016-06-29; https://www.clinicaltrials.gov/study/NCT02834637.